Milter-greylist

Milter-greylist's license consists of 3 clauses but not a so-called
3-clause BSD. "[23]-clause BSD" usually implies GPL compatibility, but
milter-greylist is not. We have three options:

1. Call its license as "BSD-variant open source license". No legal
problem but a bit of complexity.

2. Add the following clause. Moderate legal problems.
  4. Neither the name of Emmanuel Dreyfus nor the names of
     its contributors may be used to endorse or promote products
     derived from this software without specific prior written
     permission.

3. Remove the following clause. I'm not sure it is legal to remove a
license restriction without agreements of all code-level contributors.
Fortunately, this clause does not seem to refer any legal rights or
owes of any contributors other than the original author.
  3. All advertising materials mentioning features or use of this
     software must display the following acknowledgement:
         This product includes software developed by Emmanuel Dreyfus